# US 2008/0186334 A1 · Field Sequential Display of Color Images > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2008/0186334 A1 - Document ID: US20080186334A1 - Status: Published application - Kind: A1 - Application number: 11/722,706 - Filed: 2005-12-23 - Published: 2008-08-07 - Earliest claimed: 2004-12-23 - Assignees: The University of British Columbia - Inventors: Helge Seetzen - Web page: https://patentgrep.com/patent/US20080186334A1 ## CPC - G09G 3/3413: {Details of control of colour illumination sources} - G09G 3/2003: {Display of colours (specific for liquid crystal displays G09G3/3607)} - G09G 3/342: {using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines} - G09G 3/3426: {the different display panel areas being distributed in two dimensions, e.g. matrix} - G09G 3/36: using liquid crystals - G09G 2300/023: Display panel composed of stacked panels - G09G 2310/0235: Field-sequential colour display - G09G 2320/0646: Modulation of illumination source brightness and image signal correlated to each other - G09G 2320/0666: for control of colour parameters, e.g. colour temperature - G09G 2360/16: Calculation or use of calculated indices related to luminance levels in display data - G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00) ## Abstract A color display has a monochrome modulator. An active area of the modulator is illuminated by an array of light sources. The light sources include light sources of three or more colors. The intensities of the light sources may be adjusted to project desired luminance patterns on an active area of the modulator. In a fast field sequential method different colors are projected sequentially. The modulator is set to modulate the projected luminance patterns to display a desired image. In a slow field sequential method, colors are projected simultaneously and the modulator is set to modulate most important colors in the image. ## Claims ### Claim 1 A method for displaying images at a viewing area, the method comprising: providing an array comprising a plurality of groups of individually-controllable light sources, the light sources of each group emitting light of a corresponding one of a plurality of colors; driving the array in response to image data such that each of the groups projects a luminance pattern onto an active area of a modulator comprising a plurality of pixels; and, controlling the pixels of the modulator to selectively allow light from the active area to pass to the viewing area. ### Claim 2 (depends on 1) A method according to claim 1 comprising, in a first time interval, controlling the pixels of the modulator to have first modulator values based upon values specified in the image data for a first one of the colors and, in a second time interval, controlling the pixels of the modulator to have second modulator values based upon values specified in the image data for a second one of the colors. ### Claim 3 (depends on 2) A method according to claim 2 comprising generating the first modulator values by steps that include: determining a first light-source-driving signal for a first one of the groups of light sources in the array corresponding to the first color, the first light-source-driving signal based on the values specified in the image data for the first color; estimating a first luminance pattern that would be produced on the modulator by driving the first group of light sources with the first light-source-driving signal; and, computing the first modulator values based upon the values specified in the image data for the first color and the first luminance pattern. ### Claim 4 (depends on 3) A method according to claim 3 wherein computing the first modulator values comprises dividing the values specified in the image data for the first color by corresponding intensities of the first luminance pattern. ### Claim 5 (depends on 2) A method according to claim 2 comprising, during the first time interval, operating the groups of light sources corresponding to both of the first and second colors. ### Claim 6 (depends on 5) A method according to claim 5 comprising, during the second time interval, operating the groups of light sources corresponding to both of the first and second colors. ### Claim 7 (depends on 5) A method according to claim 5 comprising determining a second light source driving signal for a second one of the groups of light sources in the array corresponding to the second color, the second light-source-driving signal based on the values specified in the image data for the second color and the first modulator values. ### Claim 8 (depends on 7) A method according to claim 7 wherein determining the second light-source-driving signal comprises dividing the values specified in the image data for the second color by the first modulator values. ### Claim 9 (depends on 8) A method according to claim 8 comprising, during the first time interval, driving the second group of light sources with the second light-source-driving signal. ### Claim 10 (depends on 7) A method according to claim 7 comprising, during the second time interval driving the second group of light sources with the second light-source-driving signal. ### Claim 11 (depends on 7) A method according to claim 7 comprising, during the second time interval driving the second group of light sources with a new light-source-driving signal different from the second light-source-driving signal. ### Claim 12 (depends on 11) A method according to claim 11 comprising generating the new light-source-driving signal from the values specified in the image data for the second color. ### Claim 13 (depends on 7) A method according to claim 7 comprising generating the second modulator values by steps that include: determining a set of correction factors for the second color based upon a difference between the values specified in the image data for the second color and estimated light output values for the second color in the first time interval; and generating the second modulator values based at least upon the values specified in the image data for the second color, the correction factors, and an estimated luminance pattern for the second color. ### Claim 14 (depends on 13) A method according to claim 13 wherein the set of correction factors include correction factors for each pixel in an area of the modulator. ### Claim 15 (depends on 13) A method according to claim 13 wherein generating the second modulator values comprises setting the second modulator values so that the second modulator values do not differ from the first modulator values by more than a threshold amount. ### Claim 16 (depends on 13) A method according to claim 13 wherein generating the second modulator values comprises setting the correction factors so that the correction factors do not exceed a threshold amount. ### Claim 17 (depends on 2) A method according to claim 2 comprising, during at least one of the first and second time intervals, operating a third one of the groups of light sources to create on the modulator a luminance pattern in a third color. ### Claim 18 (depends on 17) A method according to claim 17 comprising, in a third time interval, subsequent to the second time interval, controlling the pixels of the modulator to have third modulator values based upon values specified in the image data for the third color. ### Claim 19 (depends on 2) A method according to claim 2 comprising, ranking the colors in order of importance wherein the first color is determined to be more important than other ones of the plurality of colors. ### Claim 20 (depends on 19) A method according to claim 19 wherein ranking the colors comprises identifying the one of the colors for which the image data specifies a greatest average pixel value. ### Claim 21 (depends on 19) A method according to claim 19 wherein ranking the colors comprises identifying the one of the colors for which the image data specifies a greatest average brightness. ### Claim 22 (depends on 19) A method according to claim 19 wherein ranking the colors comprises identifying the one of the colors for which the image data specifies a greatest individual pixel value. ### Claim 23 (depends on 19) A method according to claim 19 wherein ranking the colors comprises identifying the one of the colors for which the image data specifies a greatest individual pixel brightness. ### Claim 24 (depends on 19) A method according to claim 19 wherein ranking the colors comprises identifying the one of the colors for which the image data specifies a greatest variation in pixel values. ### Claim 25 (depends on 19) A method according to claim 19 wherein ranking the colors comprises identifying the one of the colors for which the image data specifies a greatest variation in brightness. ### Claim 26 (depends on 19) A method according to claim 19 wherein ranking the colors comprises a combination of one or more of: identifying the one of the colors for which the image data specifies a greatest average pixel value; identifying the one of the colors for which the image data specifies a greatest average brightness; identifying the one of the colors for which the image data specifies a greatest individual pixel value; identifying the one of the colors for which the image data specifies a greatest individual pixel brightness; identifying the one of the colors for which the image data specifies a greatest variation in pixel values; identifying the one of the colors for which the image data specifies a greatest variation in brightness; identifying the one of the colors for which the image data specifies a maximum degree of spatial clustering; or, a combination of two or more of these. ### Claim 27 (depends on 19) A method according to claim 19 wherein the first and second time intervals occur within a cycle that is repeated and wherein, during each cycle, none of the modulator values are based upon the values specified by the image data for at least a least important one of the colors. ### Claim 28 (depends on 2) A method according to claim 2 wherein the first and second time intervals both occur in a cycle that repeats at a rate not exceeding 110 Hz. ### Claim 29 (depends on 1) A method according to claim 1 performed in a repeating cycle wherein the cycle comprises a plurality of time intervals with one of the time intervals corresponding to each one of the plurality of colors wherein, for each of the time intervals, the method comprises: operating the group of light sources corresponding to the color to provide a luminance pattern on the modulator; and, controlling the pixels of the modulator to have modulator values based upon values specified in the image data for the corresponding color. ### Claim 30 (depends on 29) A method according to claim 29 wherein the cycle is repeated at a rate of at least 50 Hz. ### Claim 31 (depends on 1) A method according to claim 1 comprising, identifying a most important one of the plurality of colors; and, in a cycle comprising a plurality of time intervals, in one of the time intervals operating only the group of light sources corresponding to the most important color to provide a luminance pattern on the modulator; and, controlling the pixels of the modulator to have modulator values based upon values specified in the image data for the most important color; and in another of the time intervals, operating two or more of the groups of light sources to provide a corresponding plurality of overlapping luminance patterns on the modulator; and controlling the pixels of the modulator to have modulator values based upon values specified in the image data for colors corresponding to one of the two or more groups of light sources being operated. ### Claim 32 (depends on 1) A method according to claim 1 performed separately for each of a plurality of parts of the modulator, each of the parts comprising a plurality of pixels of the modulator. ### Claim 33 (depends on 17) A method according to claim 17 wherein the image data comprises red, green, and blue color values. ### Claim 34 (depends on 1) A method according to claim 1 wherein the image data comprises video data comprising a plurality of frames and the method is repeated for each of the frames of the video data. ### Claim 35 Apparatus for displaying images at a viewing area, the apparatus comprising: an array comprising a plurality of groups of individually-controllable light sources, the light sources of each group emitting light of a corresponding one of a plurality of colors; a modulator having an active area comprising a plurality of pixels, the active area illuminated by the array, each pixel controllable to vary a proportion of light incident on the active area that is passed to the viewing area; and, a control circuit configured to drive each of the groups of the light sources according to a control signal to project a luminance pattern onto the active area of the modulator, the luminance pattern for each of the groups having a variation in intensity over the active area. ### Claim 36 (depends on 35) Apparatus according to claim 35 wherein the modulator is a transmissive modulator. ### Claim 37 (depends on 36) Apparatus according to claim 36 wherein the modulator comprises an LCD panel. ### Claim 38 (depends on 37) Apparatus according to claim 37 wherein the LCD panel is a grey scale LCD panel. ### Claim 39 (depends on 35) Apparatus according to claim 35 wherein the modulator is a reflective modulator. ### Claim 40 (depends on 35) Apparatus according to claim 35 comprising at least three groups of light sources. ### Claim 41 (depends on 40) Apparatus according to claim 40 wherein the three groups of light sources include a red group of light sources that emit red light, a green group of light sources that emit green light and a blue group of light sources that emit blue light. ### Claim 42 (depends on 35) Apparatus according to claim 35 wherein the light sources comprise light-emitting diodes. ### Claim 43 (depends on 35) Apparatus according to claim 35 wherein two or more of the groups of light sources are made up of different numbers of light sources. ### Claim 44 (depends on 43) Apparatus according to claim 43 wherein the light sources of each of the groups of light sources are evenly distributed relative to the modulator. ### Claim 45 (depends on 35) Apparatus according to claim 35 wherein point spread functions of adjacent ones of the light sources within each of the groups overlap with one another. ### Claim 46 (depends on 45) Apparatus according to claim 45 wherein, a ratio of an average spacing between adjacent ones of the light sources in any one of the groups of light sources to a width of a point spread function of the light sources in the group of light sources is the same within ±20% for all of the groups of light sources in the array. ### Claim 47 (depends on 35) Apparatus according to claim 35 wherein the control circuit is configured to receive image data and, based on the image data, to generate light source driving signals for each of the groups of light sources and a modulator driving signal to control the modulator. ### Claim 48 (depends on 47) Apparatus according to claim 47 wherein the control circuit is configured to, in a first time interval, control the pixels of the modulator to have first modulator values based upon values specified in the image data for a first one of the colors and, in a second time interval, control the pixels of the modulator to have second modulator values based upon values specified in the image data for a second one of the colors. ### Claim 49 (depends on 48) Apparatus according to claim 48 wherein the control circuit is configured to generate the first modulator values by steps that include: determining a first light-source-driving signal for a first one of the groups of light sources in the array corresponding to the first color, the first light-source-driving signal based on the values specified in the image data for the first color; estimating a first luminance pattern that would be produced on the modulator by driving the first group of light sources with the first light-source-driving signal; and, computing the first modulator values based upon the values specified in the image data for the first color and the first luminance pattern. ### Claim 50 (depends on 48) Apparatus according to claim 48 wherein the control circuit is configured to, during the first time interval, operate the groups of light sources corresponding to both of the first and second colors. ### Claim 51 (depends on 50) Apparatus according to claim 50 wherein the controller is configured to operate the groups of light sources corresponding to both of the first and second colors during the second time interval. ### Claim 52 (depends on 51) Apparatus according to claim 51 wherein the processor is configured to determine a second light source driving signal for a second one of the groups of light sources in the array corresponding to the second color, the second light-source-driving signal based on the values specified in the image data for the second color and the first modulator values. ### Claim 53 (depends on 52) Apparatus according to claim 52 wherein the control circuit is configured generate the second modulator values by steps that include: determining a set of correction factors for the second color based upon a difference between the values specified in the image data for the second color and estimated light output values for the second color in the first time interval; and generating the second modulator values based at least upon the values specified in the image data for the second color, the correction factors, and an estimated luminance pattern for the second color. ### Claim 54 (depends on 35) Apparatus according to claim 35 wherein the control circuit comprises a data processor executing software instructions. ### Claim at position 55 55-56. (canceled)